1. Field of the Invention
The present invention relates to a light-receiving device and a method for producing the same.
2. Description of the Related Art
Living bodies, such as animals and plants, and substances, such as gases associated with the environment, have the characteristics of absorbing specific light in the infrared region including the near-infrared light with a wavelength of about 2 μm to 10 μm. In order to detect the absorption spectra of the substances such as gases associated with environments or organisms such as animals and plants, infrared light-receiving devices and infrared sensing devices including such infrared light-receiving devices are under development. In particular, in the near-infrared to infrared region, the photosensitivity to long-wavelength light is being improved. Here, the infrared light-receiving devices include a light-receiving layer composed of a III-V group compound semiconductor. In the light-receiving devices, a planar-type photodiode structure in which a p-n junction is formed by selective diffusion is used to reduce the dark current. In this planar-type photodiode structure, pixel isolation is achieved with a region in which impurity (for example, Zn impurity) is not diffused.
On the other hand, a mesa-type photodiode is also developed. In the mesa-type photodiode, a mesa structure is isolated by a mesa groove arranged surrounding the mesa structure. Non-Patent Literature 1 (Marshall J. Cohen; Michael J. Lange; Martin H. Ettenberg; Peter Dixon; Gregory H. Olsen. A Thin Film Indium Gallium Arsenide Focal Plane Array for Visible and Near Infrared Hyperspectral Imaging, Proceedings of the LEOS '99, IEEE Lasers and Electro-Optics Society 1999 12th Annual Meeting Conference, pp. 744-745) and Patent Literature (Japanese Unexamined Patent Application Publication No. 2001-144278) report two-dimensional near-infrared InGaAs image sensors including the mesa-type photodiodes in contrast with the planar-type photodiodes. Furthermore, Non-Patent Literature 2 (Mark Itzler. Low-Noise Avalanche Photodiodes for Midwave Infrared (2 to 5 μm) Applications, Princeton Lightwave Inc., Final Report, 14 Aug. 2005) reports a method for forming the mesa structure including the light-receiving layer having a type-II multi-quantum well (MQW) structure to extend sensitivity to longer wavelengths from the near-infrared region. Specifically, the Non-Patent Literature 2 reports wet etching with a phosphoric acid-based etchant to form the mesa structure.